1. Field of the Invention
The present invention relates generally to a color photographic material and, more particularly, it relates to a color photographic film capable of recording sound.
In general, as systems of recording sound images on color photographic films used in movies or television, there are an optical recording system and a magnetic recording system and the present invention relates to a color photographic film suitable for the optical recording system.
2. Description of the Prior Art
Sounds recorded in color print films, color reversal films, color reversal print films, etc., used in the fields of movies or television are reproduced by converting the sound signals recorded in the film as changes in density or area into light signals, converting the light signals into electric signals by means of a photoacceptor, and further converting the electric signals into sound signals again. As the photoacceptor used in the sound reproduction steps, photoelectric tubes having various spectral characteristics are used. Among them, a so-called S-1 type photoelectric tube is most frequently used and this photoelectric tube has a spectral sensitivity maximum at about 800 m.mu. in the infrared region (see, e.g., Adrin Cornwell Clyne, Color Cinematography, page 593 (1951)).
On the other hand, the main absorptions of the dyes formed by the coupling of color couplers and the oxidation product of a developing agent such as a para-phenylenediamine in color photographic materials for substractive color processes are all in the visible spectral region and those absorption spectral regions do not coincide with the spectral characteristics of the above-described photoelectric tube. Accordingly, if such dye images only formed by coupling are utilized for sound recording or reproduction, the sound output is too weak for practical use. Therefore, in order to conduct sound reproduction in color photographic materials, silver images or silver sulfide images are formed on recording tracks of the color photographic materials in the processing steps of the materials and the changes in density of the silver images or silver sulfide images in the infrared regions are utilized for the reproduction of sound. The infrared density (transmission density) in this case is usually about 1.0 or 1.6.
The formation of recording tracks in color print films are ordinarily conducted using the treatment as shown in, for instance, Journal of the Society of Motion Picture and Television Engineers, Vol. 77, 1054 (1968).
According to the process referenced above, the dye images in the image portions and the sound images in the sound recording portions are formed simultaneously by color development. That is to say, the unexposed silver halide in the color photographic films is removed in a first fixing bath and the developed silver formed in the development step is rehalogenated in a bleach bath. In the sound development step, a viscous sound developer is selectively coated on the sound recording portion of the color photographic film, whereby the silver halide at the sound recording portions only is converted into silver images. The silver halide at the image portions is removed in a second fixing bath and the dye images are stabilized in a stabilization bath. The density of the thus formed silver images in the sound recording track in the infrared region is utilized for the reproduction of sound.
Such a conventional system of producing sound recording tracks for color photographic films requires the step of forming silver images or silver sulfide images. Such a treatment of forming sound tracks is a step additionally required in addition to the steps of forming dye images in the image-forming portions. Such a sound recording track comprising silver or silver sulfide is formed since, as indicated above, the spectral sensitivity characteristics of the photoelectric tube used for the reproduction of sound has a sensitivity maximum in the infrared region, while the coupled dyes formed by the color development process do not have sufficient densities in this wave length region. The step of forming silver images or silver sulfide images in the sound recording tracks is additionally required besides the steps of forming dye images at the image portions as described above also and thus a method of forming sound images without the necessary for such a specific treatment step has been demanded.
As a means for resolving this problem, a color photographic material has been proposed which has a subsidiary silver halide emulsion layer containing a compound having the property of greatly reducing the bleaching speed in the bleaching step for the color photographic material or substantially destroying the bleaching action or containing a compound having the property of causing a bleaching action in only the initial period of the bleaching step to a definite bleaching extent and causing no further bleaching. Such a compound which suppresses or interrupts the bleaching action is hereinafter called a "bleach inhibitor".
However, such a color photographic material as proposed above requires a layer for the sound recording track in addition to the ordinary layers for providing dye images, which results in an increase in cost for the materials as well as for production. Also, the provision of sensitivity to such a layer for sound recording is accompanied by difficulties in that the sensitivity of the layer is reduced to less than those of the layers for the color images so that other images than sound images are not formed in the layer for sound recording and that the sensitivity of the layer is in different a wave length region than those of the layers for color images. Furthermore, by forming such a layer for sound recording, the thickness of the entire color photographic material increases and the sharpness of the color images formed in the color photographic material having such a sound recording layer tends to be reduced due to light scattering.